Hi, looks after a armeniacum?
I think the winter will have a very cool "rest".
My plants are at the moment at 12 ° C in the greenhouse and are almost nearly dry.
If the winters are warm, they do not grow - i think - .
If the damage comes from the tip of the leaf, I suspect a root problem.
Too much water, or water that is too hard or has too much fertilizer.
The water i use for the Paph. has average 250 µS. (including fertilizer, without 50-80 µS).
In this case, I would repot into fresh substrate, then only "Iron dry" and only with rainwater without fertilizer until the roots are OK again.
hope this helps
Bernd